Original post by: Lxixboss ,
I was experiencing the same problem with my mid-2010 15.4-inch Macbook Pro with Nvidia GT330M. I could also toggle the effect on and off by pressing on the palmrest just to the left of the trackpad. I found and fixed the problem 100% and I hope this can help others. It turns out that the Macbook had had its motherboard removed previously and had been reassembled incorrectly. When the motherboard is removed, the microphone typically stays glued to the case just to the left of the trackpad. When the motherboard is re-inserted, the cylindrical microphone housing does not go back into its hole in the speaker correctly. This can be verified by the fact that the motherboard does not lay flat and is elevated by a few milimeters right where the motherboard screw beside the keyboard ribbon cable is. Typically, users will just tighten this screw thereby forcing the motherboard back down into place. What this does, however, is that it slightly deforms the motherboard since the improperly inserted microphone acts as a fulcrum. It seems that this is enough to stress some solder joint or trace somewhere thereby causing the pink/green screen effect. The solution? Unglue the microphone from the palmrest area and properly insert it into its nook in the speaker. Either that or don't tighten the motherboard screw beside the keyboard ribbon cable. That is what I did and now the pink (on white) and green (on black) screen artifacts no longer occur. I'm not saying that this will work in all cases but it did in mine and maybe it will also work for you.